Broadly stated, this research project has two goals. First, I plan to investigate behavioral, neurophysiological, neuroanatomical, and neurochemical aspects of analgesia produced by focal electrical stimulation of the brain and to compare this phenomenon to analgesia produced by morphine micro-injection. Some of the specific goals subsumed under this project include: 1) To precisely describe the neuroanatomical pathways utilized and the ultimate sites and mechanisms of analgesic action. 2) To further describe the involvement of endogenous opiate substances in analgesia resulting from certain environmental manipulations. 3) To examine the functional neurochemistry of narcotic and non-narcotic analgesia systems. 4) To examine behavioral manifestations of tolerance and physical dependence to the analgesia produced by these procedures and to relate these findings to the general problem of opiate addiction. 5) To be able to suggest new and practical treatment procedures for difficult or intractable pain syndromes in man. Secondly, I proposed to identify, employing electrophysiological techniques, brain areas with behaviorally significant involvement in pain perception. Stimulation-produced analgesia, morphine analgesia, and behavioral manipulation of pain perception will be utilized as tools to achieve this goal.